Re: package.el: bytecode portability across emacs versions

[Richard Stallman]

    Emacs is not well-equipped to have source and byte code in different
    directories.  For example, it messes with the load path order: Emacs
    will prefer loading an .el file in an earlier place in the load-path
    over a .elc file in a later place.

That is not a problem for this approach, because the directory for the
specific version always comes before the version-independent directory.

    It also stops byte-recompile-directory from working and makes
    list-load-path-shadow complain.

It would be a bit strange to use byte-recompile-directory 
on these directories, though.